git clone
cd stimulus-starter
yarn install
yarn start
gnome-open http://localhost:9000/

Magic keywords

  • data-controller='hello' controller that is defined in hello_controller.js. Each dash corresponts to underscore (or dash) in file name, two dashes corresponds to subfolder users--list-item -> users/list_item_controller.js
  • data-action='click->hello#greet' event name is click, controller hello method greet. If element is <a>, <button>, <input type="submit"> than you do not need to write click. <input>, <select> and <textarea> has change as default event. <form> has submit default event. If you want to event.preventDefault() (for example click on link) than pass parameter greet(event) {}
  • data-target='' creates nameTarget property in a controller so we can use it to set value. We need to declare it also inside controller static targets = [ 'name' ]. Beside this.nameTarget you can check if there are more targets like this this.nameTargets or if exists at all this.hasNameTarget (return true or false)
  • data-hello-index='1' used to pass data to controller which you can get on initialize instead of this.element.getAttribute('data-hello-index')) you can use stimulus shorthand'index'). Also'index') to check if data existis and'index', 2) to set data so controller do not need to store any data, just use setter and getter to store data in DOM.


// src/controllers/hello_controller.js
import { Controller } from "stimulus"

export default class extends Controller {
  // triggered when controller is connected to the document
  // you can add classes to element
  connect() {
  // anytime when controller is disconnected from the dom
  disconnect() {}
  // initialize is once when controller is first instantiated
  initialize() {

  showCurrentSlide() {
    this.slideTargets.forEach((el, i) => {
      el.classList.toggle("slide--current", this.index == i)

  # getter
  get index() {
    return parseInt('index'))

  # setter
  set index(value) {'index', value)